The present invention relates to novel substituted amides useful as pharmaceutical agents, to methods for their production, to pharmaceutical compositions which include these compounds and a pharmaceutically acceptable carrier, and to a pharmaceutical method of treatment. More particularly, the novel compounds of the present invention lower low density lipoprotein choesterol (LDL) and elevate high density lipoprotein cholesterol (HDL). Both of these effects afford protection from coronary heart disease.
The atheromatous plaque, which is the characteristic lesion of atherosclerosis, results from deposition of plasma lipids, mainly cholesteryl esters, in the intima of the arterial wall. Progressive enlargement of the plaque leads to arterial constriction and ultimately coronary heart disease. Two recent clinical trials have shown a causal relationship between serum levels of LDL- and HDL-cholesterol and coronary heart disease.
In 1984, the Lipid Research Clinics-Coronary Prevention Trial (LRC-CPPT) demonstrated for the first time that lowering LDL cholesterol would reduce coronary heart disease. Very recently the results of a five-year, 4,081-patient clinical trial published in the New England Journal of Medicine, 317, pp 1237-1245 (1987) demonstrated that the lipid regulating drug, gemfibrozil, reduced the rate of heart attack and sudden cardiac death by 34 percent in patients with elevated cholesterol levels. Gemfibrozil both lowers LDL and elevates HDL; but if the results from the LRC-CPPT study are utilized to estimate the expected reduction in incidence of heart attack and heart disease due to lowering of LDL, it amounts to approximately one-half of the effect actually observed. Thus, there appears to be little doubt as to the benefit of elevating HDL.
The compounds of this invention combine two mechanisms of action to achieve their improved activity in lowering LDL and elevating HDL. Not only do they show the same effects as gemfibrozil but, in addition, they inhibit the enzyme acyl-CoA:cholesterol acyltransferase (ACAT).
Dietary cholesterol is absorbed from the intestinal lumen as free cholesterol which must be esterified with fatty acids. This reaction is catalyzed by ACAT. The resulting cholesteryl esters are packaged into the chylomicrons which are secreted into the lymph. Inhibitors of ACAT not only prevent absorption of dietary cholesterol but also prevent the reabsorption of cholesterol which has been released into the intestine through endogenous regulatory mechanisms, thus lowering LDL cholesterol levels and ultimately preventing the further development of atherosclerosis.
Prior work on amides of gemfibrozil (US 4,413,011 to Sircar, I and Holmes, A, issued November 1, 1983) identified those compounds that retained the original lipid modulating activity of the parent drug which is demonstrated by the elevation of HDL in rats. The present compounds differ in that they have been chosen for their superior inhibition of ACAT, and thus they possess two different mechanisms of action that complement each other. Thus, gemfibrozil speeds up the metabolism of LDL in the liver, and the excess cholesterol is released into the intestines via the bile. Normally a portion of this cholesterol is reabsorbed and ultimately recirculated in the form of new LDL. However, this is prevented in the presence of an ACAT inhibitor.